Both very anabolic. So sides are few. Some people have problems with Deca because it shuts them down and post cycle recovery takes longer. Also libido issues arise for many.
I ran a cycle where the first half I ran Deca and the second half EQ.
Deca causes you to retain some water. Running EQ at the end reduces the water retention at the end. Also, using deca for only 5 weeks at 300-400mg might reduce the issues.
For me this approach worked, I will likely run deca at the beginning of my cycle next time.